Conventional methods for removing adhesive residues, e.g., associated with the removal of vinyl decals from hard surfaces, e.g., auto, truck, bus, railroad, marine, aircraft bodies, and the like, are often time consuming, expensive, inefficient, and require the use of environmentally hazardous materials. For example, using art-recognized techniques, vinyl decals are often removed by careful application of heat via a heat gun and scraping to remove most of the decal and adhesive. A typical method of removing remaining adhesive residue is to wipe it away with a solvent-soaked rag. This method may be acceptable for cleaning small areas, but it is impractical for cleaning large areas, such as an airplane wing. Furthermore, many commercially available adhesive remover compositions contain chlorinated organic solvents such as methylene chloride or carbon tetrachloride (a CFC known to damage stratospheric ozone), or they are alkaline, containing high quantities of potassium or sodium hydroxide. Such adhesive remover compositions are undesirable for large-scale industrial use.
Recently, citrus-based solvents such as D-limonene, which is typically obtained from orange peels, have been developed, but such adhesive remover compositions are ineffective and impractical for large-scale use in industrial settings, and they frequently require multiple treatments in order to remove all adhesive residues. Additional commercial products exist that purport to be useful for removing labels, gum, masking tape, and the like from nonabsorbent surfaces. While such products may be free of halogenated organic solvents, they are nevertheless liquids, and therefore their use is limited to small-scale applications in which the liquid can be contained.
The removal of adhesive residue from the exterior surfaces of airplanes, which may be made of composite materials, present special technical problems. For example, it would be impractical to apply liquids to the underside of an airplane wing (having surface areas of up to 2000 ft2 or greater) because dripping liquid would contaminate the work area. Large volumes of free-flowing (i.e., liquid) organic solvents are undesirable because of the risk of fire or environmental contamination, protection of personnel, and the need for hazardous waste disposal. Adhesive residue removing compositions for use on the exterior surfaces of airplanes should not cause mechanical damage to adjacent or underlying structures and finishes. In addition, chemical attack or degradation of adjacent or underlying substrates and finishes including primer coatings should not occur. In order to be practical, any method of removing adhesive residues should ideally conclude with a water-based wash step, such as washing with soap and water. Furthermore, an adhesive removal method should be applicable and practical for horizontal, vertical, and overhead surfaces. The extensive use of carbon composite materials on new airplanes imposes heretofore unknown restrictions on chemical cleaning materials. Most of the cleaners, strippers, and other materials used on conventional aluminum aircraft surfaces are not compatible with composite materials.
There is no known, cost effective, environmentally compatible, or practical method or material for accomplishing removal of adhesive residues from large composite aircraft surfaces on the scale now required. There exists a need for a fast, safe, and effective process for removing adhesive residue remaining after removal a decal, appliqué, tape, etc.